Internet Engineering Task Force                             James M. Polk
Internet Draft                                              Cisco Systems
Expiration: April 10th, 2003
File: draft-polk-ieprep-scenarios-01.txt









                         IEPREP Topology Scenarios

                            October 10th, 2002





Status of this Memo

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Abstract

This memo conveys simplistically the likely topological scenarios that may
be encountered in reference to IEPREP phone calls.  These scenarios should
be used to focus the IEPREP Working Group during discussions and when
writing requirements, gap analysis and other solutions documents.





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Table of Contents

Abstract  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
1.0  Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
 1.2 Changes from -00 version . . . . . . . . . . . . . . . . . . . . .  2
 1.3 Terms and Definitions  . . . . . . . . . . . . . . . . . . . . . .  3
2.0  IEPREP Topologies  . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.1 Topology A "IP Bridging" . . . . . . . . . . . . . . . . . . . . .  3
 2.2 Topology B "IP at the Start" . . . . . . . . . . . . . . . . . . .  4
 2.3 Topology C "IP at the End" . . . . . . . . . . . . . . . . . . . .  4
 2.4 Topology D "End-to-End IP" . . . . . . . . . . . . . . . . . . . .  5
3.0 Security Considerations . . . . . . . . . . . . . . . . . . . . . .  5
4.0 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . .  5
5.0 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . . .  5
6.0 References  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
7.0 Authors Information . . . . . . . . . . . . . . . . . . . . . . . .  5


1.0     Introduction

This memo conveys simplistically the likely topological scenarios that may
be encountered in reference to IEPREP phone calls.  These scenarios should
be used to focus the IEPREP Working Group during discussions and when
writing requirements, gap analysis and other solutions documents.

There has been much confusion on the IEPREP list as well as within each
meeting about the topologies IEPREP is considering. Hopefully this
document will give each reader and author a reference set of named
architectures.

This memo attempts to be agnostic with regard to IP signaling or control
protocols (SIP, MEGACO, etc), as well as any underlying QOS mechanisms
(Diffserv, RSVP, NSIS, etc).


1.1 Motivation

Simply put, to get everyone referencing the same (named) topologies in
order to have useful and less confusing dialog to further this working
group's efforts.


1.2 Changes from -00 version

This version greatly reduces the text of the overall document by removing
all discussion of requirements and authentication & authorization. This is
not a requirements document (therefore shouldn't state any), and the A&A
text/discussion for each of the topologies, though necessary within the


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WG, has been moved to another "ieprep-topology-implications" document.


1.3 Terms and Definitions

The following acronyms need to be exploded for clarity:

      CSN = Circuit Switched Network

      GW  = Gateway (CSN to IP, or IP to CSN)


2.0 IEPREP Topologies

There are 4 often mentioned, but very little documented topologies
discussed within this WG's efforts so far. The following subsections name
and describe each of the topologies.

The 4 topologies are (quickly):

     Topology "IP Bridging"

     Topology "IP at the Start"

     Topology "IP at the End"

     Topology "End-to-End IP"


2.1 Topology "IP Bridging"

This topology is sometimes known as "IP in the Middle" of two CSNs. In
this topology, a CSN phone of any type initiates (dials) a call (session)
to another CSN phone with an IP core between the two CSNs.

This topology should simplistically look like this:


   Circuit                      Internet                    Circuit
   Switched         IP            or              IP        Switched
   Network        Ingress      IP Segment       Egress      Network
  -----------+              +--------------+              +-----------
             |    +----+    |     IP       |    +----+    |
     CSN     |    |    |    |              |    |    |    |     CSN
    Phone ------->| GW |----------------------->| GW |-------->Phone
             |    |    |    |              |    |    |    |
             |    +----+    |              |    +----+    |
  -----------+              +--------------+              +-----------

              Figure 1. Topology "IP Bridging"


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2.2 Topology "IP at the Start"

This topology has the initiating party placing (dialing) the call from an
IP Phone (PDA or computer), and the called party residing in the CSN.


                Internet                             Circuit
                   or                  CSN           Switched
               IP Segment            Ingress         Network
           -------------------+                 +---------------
                              |       +----+    |
              IP              |       |    |    |     CSN
             Phone ------------------>| GW |--------> Phone
                              |       |    |    |
                              |       +----+    |
           -------------------+                 +---------------

              Figure 2. Topology "IP at the Start"


One key aspect of this topology is where the intelligence is for any
prioritization of call/session handling. Initially, it cannot be assumed
that the CSN Ingress GW is ETS or priority-aware.


2.3 Topology "IP at the End"

This topology has the calling party placing the call from a CSN phone, and
the called party being in an IP network.


             Circuit                               Internet
             Switched                  CSN            or
             Network                  Egress       IP Segment
           -------------------+                 +---------------
                              |       +----+    |
              CSN             |       |    |    |      IP
             Phone ------------------>| GW |--------> Phone
                              |       |    |    |
                              |       +----+    |
           -------------------+                 +---------------

              Figure 3. Topology "IP at the End"









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2.4 Topology "End-to-End IP"

This topology has no circuit switched sections in the call path.


                            Internet
                               or
                           IP Network
            +-----------------------------------------+
            |                                         |
  +---------+                                         +-----------+
  |                                                               |
  |   IP                                                  IP      |
  |  Phone --------------------------------------------> Phone    |
  |                                                               |
  +---------+                                         +-----------+
            |                                         |
            +-----------------------------------------+

              Figure 4. Topology "End to End IP"


3.0 Security Considerations

This document merely suggests a common naming convention within IEPREP WG
discussions, therefore there are no special security considerations.


4.0 IANA Considerations

There are no IANA considerations within this document


5.0 Acknowledgements

To Scott Bradner and to Kimberly King for their comments and suggestions


6.0 References

none at this moment


7.0 Authors Information

James M. Polk
Cisco Systems
2200 East President George Bush Turnpike
Richardson, Texas 75082 USA
jmpolk@cisco.com


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The Expiration date for this Internet Draft is:

April 10th, 2003


















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